convection initiative discussion points what info do parametrizations & 1.5-km forecasts need?...
TRANSCRIPT
Convection Initiative discussion Convection Initiative discussion pointspoints• What info do parametrizations & 1.5-km forecasts need?
– Initiation mechanism, time-resolved cell size & updraft velocity, entrainment rate, rain & hail rate, organization mechanisms?
• What are the priorities for an observational campaign?– What was not learned from CSIP? Chilbolton or elsewhere? Focus on
initiation or subsequent evolution? Aircraft sampling? Scan strategy?
• What are the promising new ideas in parametrization?– Why is it so difficult? Is UK a suitable place to test parametrizations?
How can we use high-res models to develop parametrizations? Can we inter-compare new approaches at University & Met Office
• What are the priorities for flood forecasting?– How well are mechanisms for quasi-stationarity captured? Relative
importance of back-building/orographic triggering/dynamical forcing?
• What new datasets should be assimilated? New DA methods?• How important is microphysics, e.g. graupel & aerosol effects?• Where do we go from here?
– Scope? Funding mechanism, e.g. consortium bid? External collaboration, e.g. Leeds? Timing? Leadership of project?
Running orderRunning order• Robin Hogan• Humphrey Lean• Ross Bannister / Stefano Migliorini• Dan Kirshbaum• Alan Grant• Bob Plant• Remi Tailleux
To leave time for discussion afterwards, please aim for 7 mins + 2 mins for questions!
1. Radar sees clear-air scattering boundary-layer top (Morcrette 2007)
2. Refractivity: moisture convergence3. Doppler lidar: BL turbulence:
Initiation, BL Initiation, BL propertiesproperties
Radar BL top
Mesoscale model BL top
• 1/4-degree beam provides very high resolution cloud structure compared to smaller (e.g. mobile) radars:
Congestus
Mature cells
Dissipating cell
30 dBZiso-surface (~precip)
5 dBZ iso-surface (~cloud)
Cloud Cloud structurestructure
• Derive dissipation rate from spectral width (Chapman & Browning 2001)
Vertical windVertical wind1. Track features in horizontal velocity– Typical cell
transported 5025 Mt in 50-mins
– Counter-gradient momentum flux in lower troposphere
Vertical wind cont.Vertical wind cont.2. Line convection: assume 2D
flow and integrate continuity equation (Browning et al. 1997)
MicrophysicsMicrophysics
• Polarimetric radar measurements– Variational retrieval (Hogan 2007)...
• Can also estimate ice water content.
Rain rate Hail fraction